How can I hack HotMail/Yahoo/GeoCities… and so on…?
Such big websites don’t have known holes. If a new hole is discovered and goes public, expect it to be fixed in a few days or less. Of course, they may be vulnerable to massive DDoS (Distributed Denial of Service) attacks as anybody else. The only way would be to find an unknown weakness by yourself and exploit it (“0-day exploit”). Or, of course you can use “social hacking”, tricking the owner of the account to tell you his password, some way. Note that if it would be that easy to bypass protections, such as access someone else’s e-mails or defacing websites, that would be the end of the Internet.